Implantable medical device impedance measurement module for communication with one or more lead-borne devices

Abstract

Example techniques for communicating between two medical devices are described. One medical device may be an implantable medical device. Another medical device may be a lead-borne implantable medical device. The lead-borne implantable medical device may be referred to as a satellite. The implantable medical device may measure impedance of a path including at least two electrodes, at least one of which is on the lead, using an impedance measurement module. In some example implementations of this disclosure, the implantable medical device may also use the impedance measurement module to communicate with the satellite on the lead.

The invention claimed is: 
     
       1. A method comprising:
 generating, with a source of an impedance measurement module within a first implantable medical device, an impedance measurement signal; 
 measuring, with the impedance measurement module, an impedance of an electrical path that includes at least two electrodes based on the impedance measurement signal, wherein at least one of the electrodes is carried by a lead coupled to the first implantable medical device; 
 generating, with the source of the impedance measurement module, a threshold electrical signal transmitted from the first implantable medical device to a second implantable medical device that is carried by the lead; and 
 generating, by the second implantable medical device, a first communication signal that is derived from the threshold electrical signal for transmission to the first implantable medical device. 
 
     
     
       2. The method of  claim 1 , wherein generating the first communication signal comprises modulating the threshold electrical signal received from the first implantable medical device. 
     
     
       3. The method of  claim 2 , wherein modulating the threshold electrical signal comprises pulse width modulating. 
     
     
       4. The method of  claim 3 , wherein the pulse width modulating comprise a pull down of the threshold electrical signal at one of two pulse widths to generate the first communication signal as a binary signal. 
     
     
       5. The method of  claim 1 , further comprising generating a second communication signal, with the source of the impedance measurement module to transmit information to the second implantable medical device. 
     
     
       6. The method of  claim 1 , wherein the second implantable medical device is coupled to one of the at least two electrodes, the method further comprising:
 transmitting an electrical stimulation signal via the one of the at least two electrodes; and 
 ceasing communication with the second implantable medical device during transmission of the electrical stimulation signal. 
 
     
     
       7. The method of  claim 1  wherein the second implantable medical device is coupled to one of the at least two electrodes, the method further comprising:
 estimating when a cardiac event will occur; 
 sensing the cardiac event with the one of the at least two electrodes; and 
 ceasing communication with the second implantable medical device during the sensing of the cardiac event. 
 
     
     
       8. The method of  claim 1 , wherein the second implantable medical device is at least one of an accelerometer, a strain gauge, a pressure sensitive-capacitor, an optical perfusion sensor, an oxygen saturation sensor, an ultrasonic flow sensor, a thermistor, and an antimony electrode. 
     
     
       9. The method of  claim 1 , wherein the second implantable medical device comprises a switching device. 
     
     
       10. The method of  claim 5 , wherein the second communication signal is communicated to the second implantable medical device without disconnecting the impedance measurement module from the at least two electrodes. 
     
     
       11. An implantable medical device comprising:
 an impedance measurement module that comprises a source and is configured to generate an impedance measurement signal with the source, and measure an impedance of an electrical path that includes at least two electrodes based on the impedance measurement signal, wherein at least one of the electrodes is carried by a lead coupled to the implantable medical device; 
 a processor configured to generate, with the source of the impedance measurement module, a threshold electrical signal transmitted from the implantable medical device to a lead-borne implantable medical device that is carried by the lead; and 
 generating, by the lead-borne device, a first communication signal that is derived from the threshold electrical signal for transmission to the first implantable medical device. 
 
     
     
       12. The implantable medical device of  claim 11 , wherein the lead-borne device modulates the threshold electrical signal received from the first implantable medical device to generate the first communication signal. 
     
     
       13. The implantable medical device of  claim 12 , wherein modulating the threshold electrical signal comprises pulse width modulation. 
     
     
       14. The implantable medical device of  claim 13 , wherein the pulse width modulation comprises a pull down of the threshold electrical signal at one of two pulse widths to generate the first communication signal as a binary signal. 
     
     
       15. The implantable medical device of  claim 11 , wherein the processor is further configured to generate, with the source of the impedance measurement module, a second communication signal to transmit information to the lead-borne implantable medical device. 
     
     
       16. The implantable medical device of  claim 11 , wherein the lead-borne implantable medical device is coupled to one of the at least two electrodes, wherein the implantable medical device further comprises a signal generator configured to transmit an electrical stimulation signal via the one of the at least two electrodes, and wherein the processor is configured to cease communication with the lead-borne implantable medical device during transmission of the electrical stimulation signal. 
     
     
       17. The implantable medical device of  claim 11 , wherein the lead-borne implantable medical device is coupled to one of the at least two electrodes, wherein the processor is further configured to estimate when a cardiac event will occur, wherein the implantable medical device further comprises a sensing module configured to sense the cardiac event with the one of the at least two electrodes, and wherein the processor is configured to cease communication with the lead-borne implantable medical device during transmission of the electrical stimulation signal. 
     
     
       18. The implantable medical device of  claim 11 , wherein the implantable medical device is implanted within a patient. 
     
     
       19. The implantable medical device of  claim 15 , wherein the processor is configured to communicate the second communication signal without disconnecting the impedance measurement module from the at least two electrodes. 
     
     
       20. A medical system comprising:
 a lead-borne implantable medical device that is carried by a lead; 
 an implantable medical device coupled to the lead-borne medical device via the lead, the implantable medical device comprising:
 an impedance measurement module that comprises a source and is configured to generate an impedance measurement signal with the source, and measure an impedance of an electrical path that includes at least two electrodes based on the impedance measurement signal, wherein at least one of the electrodes is carried by a lead coupled to the implantable medical device; and 
 a processor configured to generate, with the source of the impedance measurement module, a threshold electrical signal transmitted from the implantable medical device to the lead-borne implantable medical device that is carried by the lead, wherein the lead-borne device generates a first communication signal derived from the threshold electrical signal for transmission to the first implantable medical device. 
 
 
     
     
       21. The medical system of  claim 20 , wherein generating the first communication signal comprises modulating the electrical signal received from the implantable medical device. 
     
     
       22. The medical system of  claim 21 , wherein the modulating the electrical signal comprises pulse width modulation. 
     
     
       23. The medical system of  claim 22 , wherein the pulse width modulation comprises a pull down of the electrical signal at one of two pulse widths to generate a binary communication signal. 
     
     
       24. The medical system of  claim 20 , the processor is further configured to generate, with the source of the impedance measurement module, a second communication signal to transmit information to the lead-borne implantable medical device. 
     
     
       25. The medical system of  claim 20 , wherein the lead-borne implantable medical device is coupled to one of the at least two electrodes, wherein the implantable medical device further comprises a signal generator configured to transmit an electrical stimulation signal via the one of the at least two electrodes, and wherein the processor is configured to cease communication with the lead-borne implantable medical device during transmission of the electrical stimulation signal. 
     
     
       26. The medical system of  claim 20 , wherein the lead-borne implantable medical device is coupled to one of the at least two electrodes, wherein the processor is further configured to estimate when a cardiac event will occur, wherein the implantable medical device further comprises a sensing module configured to sense the cardiac event with the one of the at least two electrodes, and wherein the processor is configured to cease communication with the lead-borne implantable medical device during transmission of the electrical stimulation signal. 
     
     
       27. The medical system of  claim 20 , wherein the lead-borne implantable medical device is at least one of an accelerometer, a strain gauge, a pressure sensitive-capacitor, an optical perfusion sensor, an oxygen saturation sensor, an ultrasonic flow sensor, a thermistor, and an antimony electrode. 
     
     
       28. The medical system of  claim 20 , wherein the lead-borne implantable medical device comprises a switching device. 
     
     
       29. The medical system of  claim 20 , wherein the implantable medical device is implanted within a patient, and the lead-borne implantable medical device is implanted within the patient. 
     
     
       30. The medical system of  claim 24 , wherein the processor is configured to generate the second communication signal for transmission to the lead-borne device without disconnecting the impedance measurement module from the at least two electrodes. 
     
     
       31. A computer-readable storage medium comprising instructions that cause one or more processors, within an implantable medical device, to:
 generate, with a source of an impedance measurement module within the implantable medical device, an impedance measurement signal; 
 measure, with the impedance measurement module, an impedance of an electrical path that includes two electrodes based on the impedance measurement signal, wherein at least one of the electrodes is carried by a lead coupled to the implantable medical device; 
 generate, with the source of the impedance measurement module, a threshold electrical signal transmitted from the implantable medical device to a lead-borne implantable medical device that is carried by the lead; and 
 generating, by the lead-borne implantable medical device, a communication signal derived from the threshold electrical signal for transmission to the first implantable medical device.